To provide a detector such as a neutron detector in a core of a pressurized water reactor (PWR), the detector is guided into the core by an instrumentation guide tube inserted into the core. As a method for inserting the instrumentation guide tube into the core, a bottom insertion method in which an instrumentation guide tube is inserted from bottom to top of a reactor vessel has been employed. At present, a top insertion method in which an instrumentation guide tube is inserted from top to bottom of a reactor vessel has been studied.
FIG. 51 is a schematic of an inserted state of an instrumentation guide tube, when the top insertion method is employed. As shown in FIG. 51, after inserted into a reactor vessel (not shown) from the top of the reactor vessel, an instrumentation guide tube 1 is sequentially inserted through a hollow upper core support column 4 interposed between an upper core support plate 2 and an upper core plate 3 in the reactor vessel, and an opening portion 3a of the upper core plate 3 from top to bottom, and a lower end 1a is inserted into a core 5. A neutron detector 8 is guided from top to bottom by the instrumentation guide tube 1, with a cable 9 connected to the neutron detector 8, and inserted into the core 5.
Patent Document 1: Japanese Examined Utility Model Application Publication No. H06-00798
Patent Document 2: Japanese Patent No. 2521331
Patent Document 3: Japanese Patent Application Laid-open No. H2-201193
Patent Document 4: Japanese Patent Application Laid-open No. H9-80188